forging new generations of engineers. organics metals and alloys polymers ceramics composites
TRANSCRIPT
Forging new generations of engineers
• Organics• Metals and
Alloys• Polymers• Ceramics• Composites
Organics are or were living organismsComposed of mostly carbon and HydrogenStructure depends on the way cells developed
not by human manipulationRenewable, sustainable Infinite varietyGenetically alterable
Metals are pure elements which comprise about three-fourths of the periodic table
Few are used in their pure form because of: Hardness; too hard or too softCost; scarcity of elementEngineers need certain characteristics that can
only be accomplished by a blending of basic elements
Metallic materials include alloys, which are combinations of metals and other elements
Possess material properties, including:high strength and toughnesshigh electrical conductancehigh thermal conductanceluster
Examplesaluminum - copper - gold - zinc - iron - lead -
nickelsilver - thorium - chromium - tin - beryllium
Consist of materials composed of two or more elements, at least one being a metal
This combination of elements gives the material a combination of properties from each element
ExamplesSteel- iron, carbon and impurity elements
such as boron copper or silicon Brass - copper, zincStainless Steel - nickel,ironMonel - nickel,copper
Ferrous Metallics - iron and alloys which contain at least 50% iron (e.g. wrought iron, cast iron, steel, stainless steel)
Nonferrous Metallics - Metallic elements other than iron (e.g. copper, lead, tin, zinc, titanium, beryllium, nickel)
Powdered (Sintered) Metals (ferrous or non-ferrous)Sometimes called sintered metal. A process of
producing small (powdered) particles which are compacted in a die and then “sintered” (applying heat below the melting point of the main component)
Examples: trigger on gun, gears, bearings, carbide tool inserts
PolymersChain-like molecule made of many (poly)
smaller molecular units (mono”mers”)Chaining (polymerization) is responsible for
the formation of natural fibers, wood, lignin, rubber, skin, bone and the tissues of animals, humans and insects
PlasticsHuman-made polymersPlastics are workable or moldable
Thermosetting plastics are formable once (e.g. epoxy, phonelic (Bakelite), polyurethane)
Thermoplastics can be heated repeatedly and formed into new shapes (e.g. polyethylene, nylon,
Plexiglas)
Elastomeramorphous (shapeless) structure consisting of long
coiled-up chains of entangled polymerscan be stretched at room temperature to at least
twice its original length and return to its original shape after the force has been removed
Process to strengthen an elastomer: vulcanizationa chemical process used to form strong bonds
between adjacent polymers to produce a tough, strong, hard rubber (automobile tires)
Crystalline compounds combining metallic and non metallic elements
The absence of free electrons make ceramics poor electrical conductors.
Because of the strength of the bonding, ceramics have high melting temperatures
Categories: Clay
Refractory
Electrical and Magnetic
Glasses
Cermets
Clay ProductsInorganic material which is shaped,
dried and fired.Examples: brick, floor and wall tiles, drainage
tile, roof tile, sewer pipe, chimney flue, china, and porcelain.
Refractory MaterialsCeramics designed to provide
acceptable mechanical or chemical properties while at high temperatures.
Most are based on stable oxides such as carbides, nitrides, and borides.
An example of a refractory is the machinable all-silica insulating tiles on the U.S. space shuttle
Electrical and Magnetic Applications Ceramics are used as resistors and heating
elements for furnaces (silicon carbide)Semiconductor properties:
Thermistors- as they heat-up allow current to flow.
Rectifiers- allow current to flow in one directionClay based ceramics for high-voltage insulators
GlassBased on silica with additives that alter the
structure or reduce the melting point, optimize optical properties, thermal stability and resistance to thermal shock
Cermets
Combinations of metals and ceramics(oxides, nitrides, or carbides) bonded together in the same way powdered metallurgy parts are made.
Examples: crucibles, jet engine nozzles
Laminar or Layer Composites - alternate layers of materials bonded together. (e.g. plywood, safety glass, Formica, bimetallic strips)
Particulate Composites - discrete particles of one material surrounded by a matrix of another material. (e.g. concrete, asphalt, powdered metals and ceramics)
Fiber-Reinforced Composites - composed of continuous or discontinuous fibers embedded in a matrix of another material. (e.g. Kevlar, rayon, steel reinforced tires, fiberglass, graphite-epoxy)
• Organics• Metals and Alloys• Polymers• Ceramics• Composites
Major Categories of Materials